For the past five years, the rates of adolescent drug use and treatment participation have been about twice what they were in the early 1990s. While participating in three or more months of treatment is generally associated with better outcomes, less than 20 percent of adolescents stay this long in outpatient treatment (where 80 percent of adolescents are treated). Not surprisingly, rates of relapse are high. This application builds on prior adolescent treatment and continuing care studies with an experiment that has already begun under a SAMHSA initiative. Specifically, this application seeks funds to strengthen and complete a 2 X 2 randomized field experiment. We propose to examine the impact of providing two first phase office-based outpatient interventions: a brief Motivational Enhancement Therapy/Cognitive Behavior Therapy (MET/CBT) vs. a best practice treatment as usual in Chestnut Health Systems' Outpatient Program (CHS-OP), as well as the impact of a manual-guided second phase home-based outpatient Assertive Continuing Care (ACC), which targets improving environmental and social risks, two mediators of outcome. We are particularly interested in the interaction of these conditions and will also test the cost-effectiveness of each. All the interventions are manual-based and have been previously evaluated, but this is the first time they will be directly compared in terms of their treatment effectiveness and cost-effectiveness. We propose to recruit 324 adolescents, randomly assign them to one of the four conditions, and interview them at intake, 3, 6, 9, and 12 months post intake. At intake, 3, and 12 months, we will supplement adolescent self-reports with urine testing, electronic record abstraction, and interviews with participants' parents to allow for a multi-method perspective, validation, and cost estimations. The specific aims of this study are to evaluate the relative effectiveness of: (a) MET/CBT vs. CHS-OP, (b) ACC vs. No ACC, and (c) their interaction in terms of their impact on: (1) initially reducing the frequency of substance use and problems in the first year; (2) reducing risk factors associated with relapse; and (3) Increasing the cost-effectiveness of treatment in terms of the cost per days abstinent and cost per person in recovery at month 12.